The depletion of fossil fuel reserves, global warming, energy security and the need for clean, cheap fuels has made developing sources of renewable energy a global research priority. Microbial Fuel Cells (MFCs) have the potential to generate renewable electricity from a vast array of carbon sources such as waste-water, agricultural by-products and industrial pollutants. In MFCs electrons from microbial metabolism flow from the bacteria toward an anode then on through an external circuit finally converting oxygen into water at the cathode closing the cycle. MFCs have the advantage that they can vary from micro fluidic to waste water treatment plant scale depending on the desired application.

A great deal of work has been published on optimizing microbial fuel cell electricity generation by exploring the range of carbon sources for metabolism, modifying the design and electrode composition of the fuel cell and examining the microbial community composition and structure occurring in MFCs. However there are still many obstacles that need to be overcome before this technology can be effectively put to use. The optimization of MFC systems is a highly multidisciplinary area of research and two complementary areas of work are required - firstly to design more efficient hardware for the cells by traditional engineering and secondly to understand and improve the interaction and electron transport between microbes and electrode via biological engineering.

One of the most important engineering challenges in MFC development is the efficient electron transfer from the bacteria to the anode. To date three possible methods of transferring electrons from bacterial cells to the electrode have been identified - directly via cell surface cytochromes (e.g. Shewanella spp), via pili acting as nanowires (e.g. Geobacter spp) or via the production of soluble electron mediator compounds (e.g. Pseudomonas sp phenazine production). Fundamental to cell contact with the anode, electron transfer and thus the functioning of the MFC is the formation of specialized biofilms on the electrode surface. It has been shown that the power output of MFCs and that the power density was directly dependent on biofilm growth and composition.

The objective of this proposal is to use a synthetic biology approach to reengineer bacteria to predictably and efficiently generate and transfer electrons to microbial fuel cell electrodes resulting in a highly versatile, reliable and sustainable energy sources. Synthetic biology aims to use a rigorous engineering approach to design and build new standardized biological parts, devices and systems or to reconfigure existing ones to be more efficient or to carry out new functions and has the potential to revolutionise how we conceptualise and approach the engineering of biological systems. This project aims to -

a) Create a synthetic biology toolbox of biological parts and devices for the easy engineering of electrogenic microbial strains and the construction of genetic circuits for the enhanced production of nanowire pili, surface active cytochromes and production of electron mediator compounds. b) Engineer cells to have enhanced electron transfer capabilities. c) Investigate the structure and composition electrode biofilms formed by the engineered bacteria individually, in combination with each other and their prevalence and persistence when introduced to a naturally occurring anodic biofilm derived from a variety of waste-waters. d) The versatility of carbon metabolism in the bacteria will be engineered to expand the range and efficiency of utilising pollutants as carbon sources for electricity generating metabolism closing the waste disposal energy generation loop which would be of obvious and enormous benefit to a wide range of industries.

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